Earlier it was shown that N-acetyl-D-glucosamine (NAG) causes a shift in the circular dichroic (CD) spectrum of reduced lysozyme and its carboxymethyl (CM) derivative, suggestive of a substrate binding capacity not previously known to exist in reduced lysozyme. In a continuation, N-acetyl muramic acid (NAM) has been observed to give a similar effect. However, studies on several other structurally related saccharides have shown no comparable effect; nor is this effect exhibited by other proteins, after reduction and carboxymethylation, with either NAG or NAM. Further studies on NAG indicate that this analog has also the ability to preserve both the CD spectrum and the concentration of S-methylated reduced lysozyme in solution on prolonged incubation at room temperature. Collectively, these findings suggest that a substrate molecule could combine with and alter the structural characteristics of newly synthesized protein within the living cell, prior to the major onset of chain folding, and that this interaction may contribute to the early stages of this process.